Currently submitted to: JMIR Public Health and Surveillance
Date Submitted: Sep 17, 2026
Open Peer Review Period: Sep 17, 2026 - Nov 12, 2026
(currently open for review)
Warning: This is an author submission that is not peer-reviewed or edited. Preprints - unless they show as "accepted" - should not be relied on to guide clinical practice or health-related behavior and should not be reported in news media as established information.
Did the 2026-2027 Influenza Season Begin Before South Korea’s National Vaccination Program? Evidence From Sentinel Surveillance
ABSTRACT
This research letter examined the onset of the 2026-2027 influenza season in South Korea by comparing sentinel surveillance data from its first week with seven earlier seasons. Influenza-like illness exceeded the epidemic threshold in the week beginning August 30, 2026, with the increase driven predominantly by A(H1N1)pdm09 and concentrated among children aged 1-12 years. This occurred five to eight weeks before national vaccination could first confer protection.
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